The distinction between "mere" addition, addition that changes, and rewriting, is just not that clear.This is so untenable that it is practically absurd.
By this logic, every sequel to a work of art (book, Movie or such) changes the Lore. Empire Strikes Back? Lore change. Two Towers? Lore change.
Let's go even further; every issue of a comic book changes the Lore. Every episode of a TV show changes the Lore. Every supplement, module or spin-off changes the Lore. You reduce change to a point it's a useless measurement; literally everything after the first part is Lore change.
[MENTION=22779]Hussar[/MENTION]'s Star Wars example is a good one - even when I was in primary school, I could tell that changing Luke and Leia to brother and sister cast a different light on their earlier romantic relationship.
Locking down Demogorgon's home layer, or making Mezzodaemons Blood War mercenaries, or whatever, are all changes to what came before - they fill in gaps, and add new meaning that wasn't there before.
To compare to comics: having Spider-Man stop some bank robbers is not a change to the lore, even if those particular bank robbers have never appeared in a Marvel comic before. But (say) killing of Jean DeWolff isn't just an addition (of a murder) to the fictional world; it's changing something.
What about deciding that Jean DeWolff keeps Spider-Man clippings? Well, that doesn't contradict anything, but it's clearly a change in the nature of the relationship. (A bit like the Star Wars example, though in the opposite direction.)
In any composition (visual, literary, musical) an addition can be a significant change because of the way it casts new light, or alters the relationship between, the already-established elements. I mean, would anyone deny that adding in an extra figure would change the meaning of The Last Supper?